The present invention relates to underwater acoustic detection and localization, and more particularly to a combination passive-active underwater acoustic method and apparatus for the detection and location of a surfaced or submerged object.
In the past, most acoustic mechanisms (used for example in mines or surveillance devices) were either active or passive, but not combinations of both. In the few instances wherein a combination device has been used, they have failed to provide adequate information to permit satisfactory discrimination between objects or vehicles on the water surface and those that are submerged. Moreover, some of the prior art types of mechanisms were easily countered by various types of noise generators.